Benign acute childhood myositis

Benign Acute Childhood Myositis (BACM) is a rare muscle condition that typically occurs in children following a viral infection. Characterized by sudden onset of calf pain and difficulty walking, BACM is often associated with recent episodes of influenza or other upper respiratory tract infections. Despite its acute presentation, the condition is self-limiting, with symptoms usually resolving without treatment within a few days to weeks.

Etiology

The exact cause of Benign Acute Childhood Myositis is not well understood, but it is believed to be a post-infectious complication related to viral infections. The most common viruses associated with BACM include influenza A and B, adenovirus, and enterovirus. The condition typically manifests towards the end of the infectious period, suggesting a possible immune-mediated mechanism.

Symptoms

Children with BACM present with sudden onset of bilateral calf pain, which may be severe enough to prevent walking or result in a characteristic tiptoe gait. Other symptoms may include muscle tenderness, mild fever, and general malaise. Unlike other conditions affecting the muscles, BACM does not usually involve significant weakness, myoglobinuria (presence of muscle breakdown products in the urine), or marked elevation of muscle enzymes in the blood.

Diagnosis

Diagnosis of Benign Acute Childhood Myositis is primarily clinical, based on the characteristic symptoms and history of recent viral illness. Laboratory tests may show a slight elevation in muscle enzymes such as creatine kinase (CK), but levels are typically much lower than those seen in more severe muscle diseases. Magnetic resonance imaging (MRI) and electromyography (EMG) are not routinely required but may be used to exclude other conditions if the diagnosis is uncertain.

Treatment

The management of BACM is supportive, focusing on pain relief and ensuring adequate hydration. Non-steroidal anti-inflammatory drugs (NSAIDs) may be used to alleviate pain. Children are encouraged to rest until symptoms resolve, which usually occurs within a few days to a week. Recovery is complete without any long-term complications.

Prognosis

The prognosis for Benign Acute Childhood Myositis is excellent, with children typically making a full recovery without any residual muscle damage. Recurrence is rare but has been reported.

Epidemiology

BACM is a rare condition, with outbreaks often coinciding with epidemics of influenza or other viral illnesses. It primarily affects children between the ages of 5 and 15, with a slight male predominance.

Prevention

Preventive measures for BACM are similar to those for viral infections in general, including good hand hygiene and vaccination against influenza.

NIH genetic and rare disease info

• NIH info on Benign acute childhood myositis

Benign acute childhood myositis is a rare disease.